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Lawrence Livermore’s National Ignition Facility (NIF) requires a radiation tolerant video camera to remotely monitor varied activities in and around the NIF target chamber. Our present suite of monitor cameras must be either, removed during high yield shots, requiring substantial resources or left in place which greatly reduces their life expectancy. Our goal was to develop a relatively inexpensive, radiation tolerant monitor camera which could be left in place during high yield laser experiments yet continue to give quality data for up to (5) years of operation or about 250 high yield shots. The camera was built around the CMOSIS CMV 2000 / 4000 sensor. Camera components were chosen based on their radiation tolerant performance at the Cobham radiation test facility in CO Springs. The prototype camera was tested both at Cobham and on the NIF during high yield shots. We will present test results as well as predictions for camera life expectancy.

At the National Ignition Facility, new designs for x-ray diagnostics and ICF targets place high energy density capacitors in the harsh radiation environment of the target chamber. In these applications, dielectric breakdown would be catastrophic. This study considers the behavior of three dielectric types in a prompt-dose radiation environment; aluminum electrolytic, multilayer ceramic, and metalized polypropylene. The experiments exposed the capacitors with a flash x-ray machine and measured the internal discharge from shot-to-shot for a range of doses. From the results, the thinner aluminum electrolytic dielectrics internally discharged less than the thicker ones. The results from the flash x-ray source were compared to a limited set of data taken in NIF’s neutron test-well. The aluminum electrolytic and metalized polypropylene capacitors did not fail while biased at their rated voltage during eight shots in NIF, mostly between 1e9 n/cm 2 and 4e9 n/cm 2 .

In inertial confinement fusion (ICF) experiments on the National Ignition Facility (NIF), measurements of average ion temperature using DT neutron time of flight broadening and of DD neutrons do not show the same apparent temperature. Some of this may be due to time and space dependent temperature profiles in the imploding capsule which are not taken into account in the analysis. As such, we are attempting to measure the electron temperature by recording the free-free electron-ion scattering-spectrum from the tail of the Maxwellian temperature distribution. This will be accomplished with the new NIF Continuum Spectrometer (ConSpec) which spans the x-ray range of 20 keV to 30 keV (where any opacity corrections from the remaining mass of the ablator shell are negligible) and will be sensitive to temperatures between ∼ 3 keV and 6 keV. The optical design of the ConSpec is designed to be adaptable to an x-ray streak camera to record time resolved free-free electron continuum spectra for direct measurement of the dT/dt evolution across the burn width of a DT plasma. The spectrometer is a conically bent Bragg crystal in a focusing geometry that allows for the dispersion plane to be perpendicular to the spectrometer axis. Additionally, to address the spatial temperature dependence, both time integrated and time resolved pinhole and penumbral imaging will be provided along the same polar angle. The optical and mechanical design of the instrument is presented along with estimates for the dispersion, solid angle, photometric sensitivity, and performance.

X-ray penumbral imaging has been successfully fielded on a variety of inertial confinement fusion (ICF) capsule implosion experiments on the National Ignition Facility (NIF). We have demonstrated sub-5 μm resolution imaging of stagnated plasma cores (hot spots) at x-ray energies from 6 to 30 keV. These measurements are crucial for improving our understanding of the hot deuterium-tritium fuel assembly, which can be affected by various mechanisms, including complex 3-D perturbations caused by the support tent, fill tube or capsule surface roughness. Here we present the progress on several approaches to improve x-ray penumbral imaging experiments on the NIF. We will discuss experimental setups that include penumbral imaging from multiple lines-of-sight, target mounted penumbral apertures and variably filtered penumbral images. Such setups will improve the signal-to-noise ratio and the spatial imaging resolution, with the goal of enabling spatially resolved measurements of the hot spot electron temperature and material mix in ICF implosions.

The goal of this paper is to outline the process for characterizing the S-parameters of passive two-port electrical devices to calculate the input signal from a measured output signal when standard two-port VNA measurements are not possible. For long cables such as those used at NIF to transmit analog electrical signals long distances from target diagnostics to their respective data digitizer, standard two-port VNA measurements cannot be used to determine the cables’ transfer functions due to the large physical separations between the ports of the cables. Traditionally, this problem was addressed by recording input and output waveforms with two oscilloscopes and then comparing their spectral composition. A new method is to take reflection measurements at one port and substitute three known loads at the other port to generate a system of simultaneous equations that will allow for S21 to be quantified.

The National Ignition Facility’s (NIF) harsh radiation environment can cause electronics to malfunction during high-yield DT shots. Until now there has been little experience fielding electronic-based cameras in the target chamber under these conditions; hence, the performance of electronic components in NIF’s radiation environment was unknown. It is possible to purchase radiation tolerant devices, however, they are usually qualified for radiation environments different to NIF, such as space flight or nuclear reactors. This paper presents the results from a series of online experiments that used two different prototype camera systems built from non-radiation hardened components and one commercially available camera that permanently failed at relatively low total integrated dose. The custom design built in Livermore endured a 5 × 1015 neutron shot without upset, while the other custom design upset at 2 × 1014 neutrons. These results agreed with offline testing done with a flash x-ray source and a 14 MeV neutron source, which suggested a methodology for developing and qualifying electronic systems for NIF. Further work will likely lead to the use of embedded electronic systems in the target chamber during high-yield shots.

This paper covers the preliminary design of a radiation tolerant nanosecond-gated multi-frame CMOS camera system for use in the NIF. Electrical component performance data from 14 MeV neutron and cobalt 60 radiation testing will be discussed. The recent development of nanosecond-gated multi-frame hybrid-CMOS (hCMOS) focal plane arrays by the Ultrafast X-ray Imaging (UXI) group at Sandia National Lab has generated a need for custom camera electronics to operate in the pulsed radiation environment of the NIF target chamber. Design requirements and performance data for the prototype camera system will be discussed. The design and testing approach for the radiation tolerant camera system will be covered along with the evaluation of commercial off the shelf (COTS) electronic component such as FPGAs, voltage regulators, ADCs, DACs, optical transceivers, and other electronic components. Performance changes from radiation exposure on select components will be discussed. Integration considerations for x-ray imaging diagnostics on the NIF will also be covered.

We present a characterization technique for nanosecond gated CMOS cameras designed and built by Sandia National Laboratory under their Ultra-Fast X-ray Imager program. The cameras have been used to record images during HED physics experiments at Sandia’s Z Facility and at LLNL’s National Ignition Facility. The behavior of the camera’s fast shutters was not expected to be ideal since they propagate over a large pixel array of 25 mm x 12 mm, which could result in shutter timing skew, variations in the FWHM, and variations in the shutter’s peak response. Consequently, a detailed characterization of the camera at the pixel level was critical for interpreting the images. Assuming the pixel’s photo-response was linear, the shutter profiles for each pixel were simplified to a pair of sigmoid functions using standard non-linear fitting methods to make the subsequent analysis less computationally intensive. A pixel-level characterization of a ”Furi” camera showed frame-to-frame gain variations that could be normalized with a gain mask and significant timing skew at the sensor’s center column that could not be corrected. The shutter profiles for Furi were then convolved with data generated from computational models to forward fit images collected with the camera.

Gated x-ray images through the laser entrance hole (LEH) of a hohlraum can provide critical information for ICF experiments at the National Ignition Facility (NIF), such as the size of the LEH vs time, the growth of the gold bubble 1 , and the change in the brightness of inner beam spots due to time-varying cross beam energy transfer 2 . Incorporating a high-speed multi-frame CMOS x-ray imager developed by Sandia National Laboratories 3,4 into the existing Static X-ray Imager (SXI) diagnostic5 at NIF, the new Gated LEH Imager #1 (G-LEH-1) diagnostic is capable of capturing two to four LEH images per shot on its 1024x448 pixel photo detector array, with integration times as low as 2 ns per frame. The design of this diagnostic and its implementation on NIF will be presented.

We present new designs for the launch and receiver boards used in a high speed x-ray framing camera at the National Ignition Facility. The new launch board uses a Klopfenstein taper to match the 50 ohm input impedance to the ~10 ohm microchannel plate. The new receiver board incorporates design changes resulting in an output monitor pulse shape that more accurately represents the pulse shape at the input and across the microchannel plate; this is valuable for assessing and monitoring the electrical performance of the assembled framing camera head. The launch and receiver boards maximize power coupling to the microchannel plate, minimize cross talk between channels, and minimize reflections. We discuss some of the design tradeoffs we explored, and present modeling results and measured performance. We also present our methods for dealing with the non-ideal behavior of coupling capacitors and terminating resistors. We compare the performance of these new designs to that of some earlier designs.

Geometrically enhanced photocathodes are currently being developed for use in applications that seek to improve detector efficiency in the visible to X-ray ranges. Various photocathode surface geometries are typically chosen based on the detector operational wavelength region, along with requirements such as spatial resolution, temporal resolution and dynamic range. Recently, a structure has been identified for possible use in the X-ray region. This anisotropic high aspect ratio structure has been produced in silicon using inductively coupled plasma (ICP) etching technology. The process is specifically developed with respect to the pattern density and geometry of the photocathode chip to achieve the desired sidewall profile angle. The tapered sidewall profile angle precision has been demonstrated to be within ± 2.5° for a ~ 12° wall angle, with feature sizes that range between 4-9 μm in diameter and 10-25 μm depth. Here we discuss the device applications, design and present the method used to produce a set of geometrically enhanced high yield X-ray photocathodes in silicon.

This paper covers a systems engineering analysis of existing scope-based Target Diagnostics (TD) on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL), for the purpose of selecting a standard digitizer architecture future diagnostics. Key performance criteria and a summary of test results are presented. Currently of the 60+ Target Diagnostics, at least fifteen use a type of high speed electrical signal data read-out device leading to over 200 digitization channels spread over six types of CRT and digital oscilloscopes, each with multiple models and versions. The proposed standard architecture discussed in this paper allows the NIF to efficiently and reliably operate digitizers that meet the required performance metrics for the lifetime of the NIF. The systems engineering analysis identifies key stakeholders for multiple subsets of scope-based diagnostics including but not limited to the nToFs (neutron Time of Flight), DANTE a broadband, time-resolved x-ray spectrometer, SPBT (South Pole Bang Time), GRH (Gamma Reaction History), and FFLEX (Filter Fluorescer Diagnostic). From these stakeholders, key performance metrics are derived and feed into test and evaluation criteria for different digitizers and architectures.

The 3ω scattered light polarimetry diagnostic in the 30° incidence cone backscatter diagnostic at the National Ignition Facility (NIF) is being upgraded to measure the full time-resolved Stokes vector. Previously, the diagnostic had a single channel capable of diagnosing the time-integrated balance of the horizontal and vertical polarizations. Two additional channels were added – one that measures the balance of the 45° and 135° projections, and another that measures the right- and left-circular polarizations – and together the three complete the Stokes vector measurement. A division-of-aperture scheme is employed in which three nearby portions of the near field are sampled simultaneously. Time resolution is obtained by relaying an image of the measured regions onto a set of fibers coupled to diodes. The new diagnostic will be capable of measuring scattered light signals

X-ray framing cameras based on proximity-focused micro-channel plates (MCP) have been playing an important role as diagnostics of inertial confinement fusion experiments [1]. Most of the current x-ray framing cameras consist of a single MCP, a phosphor, and a recording device (e.g. CCD or photographic films). This configuration is successful for imaging x-rays with energies below 20 keV, but detective quantum efficiency (DQE) above 20 keV is severely reduced due to the large gain differential between the top and the bottom of the plate for these volumetrically absorbed photons [2]. Recently developed diagnostic techniques at LLNL require recording backlit images of extremely dense imploded plasmas using hard x-rays, and demand the detector to be sensitive to photons with energies higher than 40 keV [3]. To increase the sensitivity in the high-energy region, we propose to use a combination of two MCPs. The first MCP is operated in low gain and works as a thick photocathode, and the second MCP works as a high gain electron multiplier [4,5]. We assembled a proof-of-principle test module by using this dual MCP configuration and demonstrated 4.5% DQE at 60 keV x-rays.

The Kirkpatrick Baez Optic (KBO) diagnostic designed for the National Ignition Facility (NIF) requires very precise alignment between four pairs of mirrors that make up four x-ray imaging channels. Furthermore, the overlapping image axis of the four pairs must be aligned to within a 50 μm radius of the NIF target center. In order to achieve this the diagnostic utilizes a telescoping snout that when extended, locates the mirrors at the end of a Diagnostic Load Package (DLP), cantilevered more than three meters out from its bolted connection points. Discussed in this paper are the structural challenges and the mechanical design solutions that were implemented to achieve the ±50 μm pointing accuracy. During an Inertial Confinement Fusion (ICF) experiment, the KBO diagnostic will be 117 mm away from the extremely high impulse, target implosion shock wave, which requires a unique approach to protecting the sensitive optics which will also be discussed.

Our paper will describe a recently designed Mk x Nk x 10 um pixel CMOS gated imager intended to be first employed at the LLNL National Ignition Facility (NIF). Fabrication involves stitching MxN 1024x1024x10 um pixel blocks together into a monolithic imager (where M = 1, 2, . .10 and N = 1, 2, . . 10). The imager has been designed for either NMOS or PMOS pixel fabrication using a base 0.18 um/3.3V CMOS process. Details behind the design are discussed with emphasis on a custom global reset feature which erases the imager of unwanted charge in ~1 us during the fusion ignition process followed by an exposure to obtain useful data. Performance data generated by prototype imagers designed similar to the Mk x Nk sensor is presented.

As neutron yields increase at the National Ignition Facility (NIF) the need for neutron ‘hardened’ diagnostics has also increased. Gated Imagers located within the target chamber are exposed to neutrons which degrade image quality and damage electronics. In an effort to maintain the signal to noise ratio (S/N) on our images and mitigate neutron induced damage, we have implemented numerous upgrades to our X-ray framing cameras. The NIF Gated X-ray Detector (GXD), design has evolved into the Hardened Gated X-ray Detector, HGXD. These improvements are presented with image data taken on high yield NIF shots showing enhanced image quality. Additional upgrades were added to remotely locate sensitive electronics and ease operational use.

We present lessons learned from the fielding of various Mach-Zehnder (MZ) based diagnostic systems on the National Ignition Facility (NIF) and potential solutions. The DANTE X-ray diagnostic is the next in a series of applications for Mach-Zehnder based signal transport and acquisition systems on NIF and as such will incorporate many of these upgrades. In addition to extended dynamic-range performance and improved reliability, the upgrades presented also enable multiplexing of the signals from DANTE’s 18 X-Ray Diodes (XRD) to economize on system cost and rack space. Previous deployments on other NIF diagnostics highlighted the necessity to decouple the input light intensity from the bias point of the Mach-Zehnder. Areas of concern including polarization, temperature, bias point and optical power level control will be addressed.

The National Ignition Facility requires a radiation-hardened, megapixel CMOS imaging sensor-based camera to be a direct physical and operational replacement for the CCD cameras currently used in x-ray streak cameras and gated imaging detectors. Camera electronics were selected to operate up to 10 krad(Si). The camera incorporates a fast dump of the sensor followed by exposure and image readout. This allows the dumping of charge due to the prompt radiation background and then readout of the longer persistence phosphor image from the x-ray diagnostics. Internal timing delays and optical performance were measured for a radiation-tolerant camera, based on the 2k by 2k CMV4000 sensor from CMOSIS Inc.

DIXI utilizes pulse-dilation technology to achieve x-ray imaging with temporal gate times below 10 ps. The longitudinal magnetic eld used to guide the electrons during the dilation process results in a warped image, similar to an optical distortion from a lens. Since the front end, where x-rays are converted into electrons at the beginning of the magnetic eld, determines the temporal resolution these distortions in uence the temporal width of the images at the back end, where it is captured. Here we discuss the measurements and methods used to reverse the magnetic warp e ect in the DIXI data. The x-ray measurements were conducted using the COMET laser facility at the Lawrence Livermore National Laboratory.

A neutron hardened x-ray streak camera has been used to report x-ray burn duration and time of peak emission from imploding ICF capsules at the National Ignition Facility with

Charge-injection devices (CIDs) are solid-state 2D imaging sensors similar to CCDs, but their distinct architecture makes CIDs more resistant to ionizing radiation. CID cameras have been used extensively for X-ray imaging at the OMEGA Laser Facility with neutron fluences at the sensor approaching 10 9 n/cm 2 (DT, 14 MeV). A CID Camera X-ray Imager (CCXI) system has been designed and implemented at NIF that can be used as a rad-hard electronic-readout alternative for time-integrated X-ray imaging. This paper describes the design and implementation of the system, calibration of the sensor for X-rays in the 3 - 14 keV energy range, and preliminary data acquired on NIF shots over a range of neutron yields. The upper limit of neutron fluence at which CCXI can acquire useable images is ~ 10 8 n/cm 2 and there are noise problems that need further improvement, but the sensor has proven to be very robust in surviving high yield shots (~ 10 14 DT neutrons) with minimal damage.

Gated X-Ray imagers have been used on many ICF experiments around the world for time resolved imaging of the target implosions. DIXI (Dilation X-ray Imager) is a new fixed base diagnostic that has been developed for use in the National Ignition Facility. The DIXI diagnostic utilizes pulse-dilation technology [1,2,3,4] and uses a high magnification pinhole imaging system to project images onto the instrument. DIXI is located outside the NIF target chamber approximately 6.5m from target chamber center (TCC). The pinholes are located 10cm from TCC and are aligned to the DIXI optical axis using a diagnostic instrument manipulator (DIM) on an adjacent port. By use of an extensive lead and poly shielded drawer enclosure DIXI is capable of collecting data at DT neutron yields up to Yn~ 10 16 on CCD readout and up to Yn~ 10 17 on film. Compared to existing pinhole x-ray framing cameras DIXI also provides a significant improvement in temporal resolution

Periodic sensitivity calibration of imaging plates (IP) is crucial for quantitative understanding of x-ray data obtained at the National Ignition Facility (NIF). To test the x-ray sensitivity of the IPs and the scanners, we developed an x-ray exposure station based on radioactive isotopes (55Fe, 109Cd, and 241Am). This apparatus provides a convenient setup for a periodical test of the IP’s and the scanners. On NIF implosion experiments with deuterium-tritium mixture fuel, the neutrons produced in the capsule hit the imaging plates and impose background signal. Therefore it is also important to know the neutron sensitivity of the IPs. The sensitivity for 14 MeV neutrons was measured on high neutron yield shots at the OMEGA laser facility. The measured sensitivities were compared with the results of Monte Carlo simulations.

Strip velocity measurements of gated X-ray imagers are presented using an ultra-short pulse laser. Obtaining timeresolved X-ray images of inertial confinement fusion shots presents a difficult challenge. One diagnostic developed to address this challenge is the gated X-ray imagers. The gated X-ray detectors (GXDs) developed by Lawrence Livermore National Laboratory and Los Alamos National Laboratory use a microchannel plate (MCP) coated with a gold strip line, which serves as a photocathode. GXDs are used with an array of pinholes, which image onto various parts of the GXD image plane. As the pulse sweeps over the strip lines, it creates a time history of the event with consecutive images. In order to accurately interpret the timing of the images obtained using the GXDs, it is necessary to measure the propagation of the pulse over the strip line. The strip velocity was measured using a short pulse laser with a pulse duration of approximately 1-2 ps. The 200nm light from the laser is used to illuminate the GXD MCP. The laser pulse is split and a retroreflective mirror is used to delay one of the legs. By adjusting the distance to the mirror, one leg is temporally delayed compared to the reference leg. The retroreflective setup is calibrated using a streak camera with a 1 ns full sweep. Resolution of 0.5 mm is accomplished to achieve a temporal resolution of ~5 ps on the GXD strip line.

At the Lawrence Livermore National Laboratory (LLNL) we are designing, developing and testing multiple Kirkpatrick-Baez (KB) optics to be added to the suite of x-ray diagnostic instruments for the National Ignition Facility (NIF). Each optic consists of four KB channels made of spherically super-polished x-ray substrates. These substrates are multilayer-coated to allow steep grazing angle geometry and wavelength filtering. These optics are customized for different experiments and will provide NIF with an alternative x-ray imaging technique to pinholes, improving both resolution and photon throughput. With this manuscript we describe KB optic requirements, specifications, optical and multilayer designs.

X-ray imaging diagnostics instruments will operate in a harsh ionizing radiation background environment during ignition experiments at the National Ignition Facility (NIF). This background consists of mostly neutrons and gamma rays produced by inelastic scattering of neutrons. An imaging system, M-ARIANE (Mirror-assisted Active Readout In A Neutron Environment), based on an x-ray framing camera with film, has been designed to operate in such a harsh neutron-induced background environment. Multilayer x-ray mirrors and a shielding enclosure are the key components of this imaging system which is designed to operate at ignition neutron yields of ~1e18 on NIF. Modeling of the neutronand gamma-induced backgrounds along with the signal and noise of the x-ray imaging system is presented that display the effectiveness of this design.

The Static X-Ray Imager (SXI) is a National Ignition Facility (NIF) diagnostic that uses a CCDcamera to record timeintegrated X-ray images of target features such as the laser entrance hole of hohlraums. SXI has two dedicated positioners on the NIF target chamber for viewing thetarget from above and below, and the X-ray energies of interest are 870 eV for the “soft” channel and 3 – 5 keV for the “hard” channels. The original cameras utilize a large formatbackilluminated 2048 x 2048 CCD sensor with 24 micron pixels. Since the original sensor isno longer available, an effort was recently undertaken to build replacement cameras withsuitable new sensors. Three of the new cameras use a commercially available front-illuminatedCCD of similar size to the original, which has adequate sensitivity for the hard X-ray channelsbut not for the soft. For sensitivity below 1 keV, Lawrence Livermore National Laboratory (LLNL) had additional CCDs back-thinned andconverted to back-illumination for use in the other two new cameras. In this paper we describethe characteristics of the new cameras and present performance data (quantum efficiency, flat field, and dynamic range) for the front- and back-illuminated cameras, with comparisons to the originalcameras.

We present evidence of an artifact in gated x-ray framing cameras that can severely impact image quality. This artifact presents as a spatially-varying, high-intensity background and is correlated with experiments that produce a high flux of x-rays during the time before the framing camera is triggered. Dedicated experiments using a short pulse UV laser that arrives before, during, and after the triggering of the framing camera confirm that these artifacts can be produced by light that arrives in advance of the voltage pulse that triggers the camera. This is consistent with these artifacts being the result of photoelectrons produced uniformly at the active area of the camera by early incident light and then selectively trapped by the electromagnetic (EM) fields of the camera. Simulations confirm that the EM field above the active surface can act to confine electrons produced before the camera is triggered. We further present a method to suppress these artifacts by installing a conducting electrode in front of the active area of the framing camera. This device suppresses artifacts by attracting any electrons liberated by x-rays that arrive before the camera is triggered.

We present performance data for Mach-Zehnder optical modulators fielded on the National Ignition Facility (NIF) as a potential signal path upgrade for the South Pole Bang Time diagnostic. A single channel demonstration system has been deployed utilizing two modulators operating in a 90° In phase and Quadrature (I/Q) configuration. X-ray target emission signals are split and fed into two recording systems: a reference CRT based oscilloscope, Greenfield FTD10000, and the dual Mach-Zehnder system. Results of X-ray implosion time (bang time) determination from these two recording systems are compared and presented.

DIXI (dilation x-ray imager) will be used to characterize ICF (inertial confinement fusion) implosions on the NIF. DIXI utilizes pulse-dilation technology 1 to achieve x-ray imaging with temporal gate times below 10 ps. Time resolved x-ray measurements were conducted using the COMET laser facility at the Lawrence Livermore National Laboratory. Here we focus on some of the challenges faced by the large aperture photo cathode of the instrument and report on how to maintain a at photo cathode as well as how the required spatial resolution of the instrument is achieved.

Gated X-Ray imagers have been used on many ICF experiments around the world for time resolved imaging of the target implosions. ARIANE (Active Readout In A Neutron Environment) has been developed for use in the National Ignition Facility and has been deployed in multiple phases. Phase 1 (complete) known as ARIANE Ultra Light (Alignment proof of concept), Phase 2a known as ARIANE Light (complete) (X-ray gated detector with electronic recording), Phase 2b (complete) (X-ray gated detector with film recording) and Phase 3 known as ARIANE Heavy which is currently under development. The ARIANE diagnostic is comprised of the following subsystems: pinhole imaging system, filtering, detector head, detector head electronics, control electronics, CCD, and film recording systems. The phased approach allows incremental increases in tolerance to neutron yield. Phase 2a and 2b have been fielded successfully and captured gated implosion images on CCD and film at neutron yields up to 7 x 10 14 . As the yields in the NIF increase Phase 3 will be a longer term solution incorporating an indirect optical path, hardened advanced detectors and significant (tons) of shielding. Design and Initial commissioning data for Phase 1-2b are presented here.

The National Ignition Facility South Pole Bang Time diagnostic uses polycrystalline diamond photoconductive detectors to measure x-ray bang time on capsule implosion shots. The original Laboratory for Laser Energetics PCD design was redesigned to eliminate ringing near the peak of the impulse response, and provide 30 picosecond resolution. The detector design, performance and x-ray laser impulse response tests used to characterize the detector are presented.

We present a new diagnostic for the National Ignition Facility (NIF) [1,2]. The Streaked Polar Instrumentation for Diagnosing Energetic Radiation (SPIDER) is an x-ray streak camera for use on almost-igniting targets, up to ~10 17 neutrons per shot. It measures the x-ray burn history for ignition campaigns with the following requirements: X-Ray Energy 8-30keV, Temporal Resolution 10ps, Absolute Timing Resolution 30ps, Neutron Yield: 10 14 to 10 17 . The features of the design are a heavily shielded instrument enclosure outside the target chamber, remote location of the neutron and EMP sensitive components, a precise laser pulse comb fiducial timing system and fast streaking electronics. SPIDER has been characterized for sweep linearity, dynamic range, temporal and spatial resolution. Preliminary DT implosion data shows the functionality of the instrument and provides an illustration of the method of burn history extraction.

The National Ignition Facility requires a radiation-hardened, megapixel CMOS imaging sensor-based camera to be a direct physical and operational replacement for the CCD cameras currently used in x-ray streak cameras and gated imaging detectors. The first phase is a radiation-tolerant camera for characterization of radiation effects on the imaging sensor. This will be followed by a fully hardened version. The radiation-tolerant camera, based on the 2k by 2k CMV4000 sensor from CMOSIS Inc., has been built and optical performance was measured. Camera parts were selected to operate up to 10 krad(Si) and the camera incorporates a fast charge and dump of the sensor pixels, followed by image readout. This allows the dumping of charge due to the prompt radiation noise and then readout of the longer persistence phosphor signal from the x-ray diagnostics.

Vendor supplied CMOS sensors were exposed to 14 MeV neutrons on yield shots in NIF and examined for damage. The sensors were exposed to multiple shots with a maximum fluence on one of the sensors of 4.3E11 n/cm2. The results of post-shot testing will be presented. LLNL is investigating the suitability of CMOS imaging sensors for use in the camera of the ARIANE diagnostic which will mitigate the effects of the NIF neutron environment by dumping photoelectrons during the neutron pulse and then recording an image stored on a long persistence phosphor.

From a point of a signal-to-background ratio, phosphors are a key component of micro channel plate (MCP) based x-ray framing cameras. In an MCP based framing camera, x-ray signal is converted to electrons, gated, amplified, and converted back to optical signal on the phosphor. To operate x-ray framing cameras in a harsh neutron induced radiation background of the National Ignition Facility, cathodeluminescence efficiency of the phosphor is very important. To avoid MCP damage due to high voltage breakdown, we have been operating phosphors below 3kV (acceleration field < 6 kV/mm). The signal-to-background ratio the camera can be significantly improved by increasing the phosphor potential to 10kV. We measured conversion efficiencies of standard phosphors at electron energies of 0.5 ~10 keV and assessed achievable performance of them with using a numerical model.

X-ray imaging is integral to the measurement of the properties of hot plasmas. To this end, a suite of gated x-ray imagers have been developed for use in a wide range of experiments at the National Ignition Facility (NIF). These instruments are sensitive to x-rays over the range of 0.7-90keV and can acquire images at 20ps intervals for source intensities ranging over several orders of magnitude. We review the design, technology, and construction of these instruments and present recent results obtained from NIF experiments in which gated x-ray imagers have played a key role. The radiation environment associated with Inertial Confinement Fusion (ICF) experiments presents unique challenges for x-ray imaging. We report on the performance of gated imagers that have been optimized for this harsh environment and describe diagnostics to be deployed in the near future that will provide x-ray images of imploding ICF capsules in the presence of backgrounds associated with neutron yields above 1016. Such images will provide crucial data that will enable even higher neutron yields and successful ignition.

The large fluence of 14-MeV neutrons produced in high-yield inertial confinement fusion (ICF) experiments creates a variety of backgrounds in x-ray imagers viewing the implosion. Secondary charged particles produce background light by Cherenkov emission, phosphor screen excitation and possibly scintillation in the optical components of the imager. In addition, radiation induced optical absorption may lead to attenuation of the signal. Noise is also produced directly in the image recorder itself (CCD or film) via energy deposition by electrons and heavy charged particles such as protons and alphas. We will present results from CCD background measurements and compare them to Monte Carlo calculations. In addition we show measurements of luminescence and long-term darkening for some of the glasses employed in imagers.

X-ray imaging instruments will operate in a harsh ionizing radiation background environment on implosion experiments at the National Ignition Facility. These backgrounds consist of mostly neutrons and gamma rays produced by inelastic scattering of neutrons. Imaging systems based on x-ray framing cameras with film and CCD's have been designed to operate in such harsh neutron-induced background environments. Some imaging components were placed inside a shielded enclosure that reduced exposures to neutrons and gamma rays. Modeling of the signal and noise of the x-ray imaging system is presented.

Phosphors are key components of x-ray framing cameras. On implosion experiments at the National Ignition Facility, the x-ray framing cameras must operate in a harsh neutron induced ionizing radiation. One promising approach of neutron induced background reduction is separation of the neutron background with using difference of x-ray and neutron time-of- flight. To complete x-ray imaging before arrival of the neutron induced radiation to the detector, it is crucial to find a phosphor which has high efficiency and fast decay time. We tested various phosphor materials to optimize design of framing cameras for implosion experiments.

The BioBriefcase is an integrated briefcase-sized aerosol collection and analysis system for autonomous monitoring of the environment, which is currently being jointly developed by Lawrence Livermore and Sandia National Laboratories. This poster presents results from the polymerase chain reaction (PCR) module of the system. The DNA must be purified after exiting the aerosol collector to prevent inhibition of the enzymatic reaction. Traditional solid-phase extraction results in a large loss of sample. In this flow-through system, we perform sample purification, concentration and amplification in one reactor, which minimizes the loss of material. The sample from the aerosol collector is mixed with a denaturation solution prior to flowing through a capillary packed with silica beads. The DNA adheres to the silica beads allowing the environmental contaminants to be flushed to waste while effectively concentrating the DNA on the silica matrix. The adhered DNA is amplified while on the surface of the silica beads, resulting in a lower limit of detection than an equivalent eluted sample. Thus, this system is beneficial since more DNA is available for amplification, less reagents are utilized, and contamination risks are reduced.

The ICF program at Livermore has a large inventory of optical streak cameras that were built in the 1970s and 1980s. The cameras include microchannel plate image-intensifier tubes (IIT) that provide signal amplification and early lenscoupled CCD readouts. Today, these cameras are still very functional, but some replacement parts such as the original streak tube, CCD, and IIT are scarce and obsolete. This article describes recent efforts to improve the performance of these cameras using today’s advanced CCD readout technologies. Very sensitive, large-format CCD arrays with efficient fiber-optic input faceplates are now available for direct coupling with the streak tube. Measurements of camera performance characteristics including linearity, spatial and temporal resolution, line-spread function, contrast transfer ratio (CTR), and dynamic range have been made for several different camera configurations: CCD coupled directly to the streak tube, CCD directly coupled to the IIT, and the original configuration with a smaller CCD lens coupled to the IIT output. Spatial resolution (limiting visual) with and without the IIT is 8 and 20 lp/mm, respectively, for photocathode current density up to 25% of the Child-Langmuir (C-L) space-charge limit. Temporal resolution (fwhm) deteriorates by about 20% when the cathode current density reaches 10% of the C-L space charge limit. Streak tube operation with large average tube current was observed by lluminating the entire slit region through a Ronchi ruling and measuring the CTR. Sensitivity (CCD electrons per streak tube photoelectron) for the various configurations ranged from 7.5 to 2,700 with read noise of 7.5 to 10.5 electrons. Optimum spatial resolution is achieved when the IIT is removed. Maximum dynamic range requires a configuration where a single photoelectron from the photocathode produces a signal that is 3 to 5 times the read noise.

Due to the planar construction of present x-ray streak tubes significant off-center defocusing is observed in both static and dynamic images taken with one-dimensional resolution slits. Based on the streak tube geometry curved photocathodes with radii of curvature ranging from 3.5 to 18 inches have been fabricated. We report initial off-center focusing performance data on the evaluation of these "improved" photocathodes in an X-ray streak camera and an update on the theoretical simulations to predict the optimum cathode curvature.

We present a new x-ray detection technique based on optical measurement of the effects of x-ray absorption and electron hole pair creation in a direct band-gap semiconductor. The electron-hole pairs create a frequency dependent shift in optical refractive index and absorption. This is sensed by simultaneously directing an optical carrier beam through the same volume of semiconducting medium that has experienced an xray induced modulation in the electron-hole population. If the operating wavelength of the optical carrier beam is chosen to be close to the semiconductor band-edge, the optical carrier will be modulated significantly in phase and amplitude. This approach should be simultaneously capable of very high sensitivity and excellent temporal response, even in the difficult high-energy xray regime. At xray photon energies near 10 keV and higher, we believe that sub-picosecond temporal responses are possible with near single xray photon sensitivity. The approach also allows for the convenient and EMI robust transport of high-bandwidth information via fiber optics. Furthermore, the technology can be scaled to imaging applications. The basic physics of the detector, implementation considerations, and preliminary experimental data are presented and discussed.

The National Ignition Facility (NIF) requested an optical diagnostic for measuring shock velocities, shock breakout times, and shock emission of objects with sizes of 1 to 10 mm. For the polar port of the target chamber, an 8-inch triplet lens collects light at f/3 inside a 30-foot-diameter vacuum chamber and uses an optical relay to send the image into two interferometers located at a distance of 160 feet. Light propagates through a VISAR (Velocity Interferometry System for Any Reflector) interferometer employing a Mach-Zehnder configuration. After exiting the interferometers the images are recorded, both by streak cameras and CCD gated imagers. Discrete magnification changes are accomplished by swapping out optical elements. Large dove prisms are used to rotate the image to align a selected region of the object with the slits of the streak cameras. Unique mounting structures are required to remotely control the alignment of the optical axis. Finite Element Analysis (FEA) was performed on all mounting structures. The first 8-inch triplet can be no closer than 500 mm from the target chamber center and is protected by a blast window that has to be replaced after every event. The first several lens groups have to be fused silica for radiation resistance. A frequency-doubled Nd:YAG laser, operating at 659.5 nm, is used to illuminate the moving object. The VISAR laser wavelength had to be different than the first, second, and third harmonics of the NIF drive lasers.

The engineering process of integrating the Petawatt (10{sup 15} watts) laser system into the existing 30 kJ (UV) Nova laser at Lawrence Livermore National Laboratory (LLNL) is described in detail. The nanosecond-long, chirped Petawatt laser pulse is initially generated in a separate master oscillator room and then injected into one of Nova`s 10 beamlines. There, the pulse is further amplified and enlarged to {approximately}{phi}60 cm, temporally compressed under vacuum to